In the bowl of a stand mixer, combine the cake
mix, instant pudding, eggs, coconut milk, canola oil, rum, pineapple juice, and
vanilla. Beat on medium speed for 2 minutes, or until smooth and
combined. Fold in the crushed pineapple and shredded coconut. Fill with
cake pans evenly. Bake in the preheated oven for 25-30 minutes or until a
toothpick inserted into the center of the cake comes out clean. Cool in
the pans for 10 minutes, then invert and cool completely on wire racks.

Meanwhile, make the coconut buttercream by
combining shortening, powdered sugar, coconut milk, meringue powder, vanilla
extract, and salt into the bowl of a stand mixer. Mix on low for 1
minute, or until combined. Then turn to medium speed and mix for another
1-2 minutes or until smooth and light, adding coconut milk as necessary to
achieve the desired consistency. Scoop about 1/3 of the frosting into a separate
bowl and stir in the shredded coconut.

Use the frosting with shredded coconut to frost
between the three layers. Use the smooth
buttercream to frost the outside of the cake and garnish with dried pineapple flowers.